Various brines exist which contain Li salts. At times, it is desired to preferentially remove and/or recover the Li ion from the brine. In some brines, such as geothermal brines or such as Smackover brines, it is often desirable to remove Li values therefrom, either because one wants the Li values in substantially pure or concentrated form or because one wants the brine to be substantially free of Li.
There are various published articles and patents dealing with Li extraction from brines.
In Israel J. Chem. Vol. 1, 1963 (pp. 115-120) there is an article by D. Kaplan titled "Process For The Extraction of Lithium From Dead Sea Solutions." There it is taught that Li is precipitated as lithium aluminate from Dead Sea brines by adding an aluminum salt and an alkali thereto.
There is a U.S. Government Publication, PB 245,686, prepared by Hazen Research, Inc. for the U.S. Department of Interior, Bureau of Mines dated June 12, 1975 and distributed by National Technical Information Service, U.S. Department of Commerce, which is titled "The Recovery and Separation of Mineral Values From Geothermal Brines." The article teaches among other things, the use of aluminum hydroxide as a precipitant for extracting Li from brine. The article also refers to U.S. Pat. Nos. 3,307,922; 3,306,712; 3,537,813; 2,964,381; and 3,306,700.
U.S. Pat. No. 3,307,922 teaches the use of an immiscible monoalkanol or ketone along with ammonia to separate lithium salts from calcium salts in a brine solution.
U.S. Pat. No. 3,306,712 is similar to 3,307,922 above except that it teaches the use of a complexing agent, e.g. urea, to form soluble complexes with the calcium in the brine.
U.S. Pat. No. 3,537,813 involves the use of a metal halide (e.g., iron, cobalt, nickel) to react with lithium in brines, adding acid to avoid hydrolysis of the metal halide, and extraction of the lithium-containing compounds into a water-insoluble organic solvent.
U.S. Pat. No. 2,964,381 teaches to separate lithium values from an aqueous solution which contains alkaline earth metal salts, by adding a soluble aluminum salt to precipitate the lithium as a lithium aluminate complex.
U.S. Pat. No. 3,306,700 enlarges on, and improves, the lithium aluminate complex process of U.S. Pat. No. 2,964,381 above.
Other patents which also help establish the state of the art of extracting lithium values from brines are, e.g., U.S. Pat. Nos. 2,980,497; 2,980,498; 2,980,499; 3,295,920; and 3,268,290.
U.S. Pat. No. 2,980,497 discloses a method of recovering the lithium from a lithium aluminate complex formed, e.g., in the process of U.S. Pat. No. 2,964,381. The method involves heating the complex in water to at least 75.degree. C. to decompose it and then using a strongly acidic cation exchange resin to bind the soluble lithium compound and impurities, subsequently treating the resin with a caustic solution to form soluble lithium hydroxide and insoluble impurities and recovering the lithium hydroxide.
U.S. Pat. No. 2,980,498 shows recovering of lithium values from ores (spodumene, lepidolite, and the like) by using a strongly acidic cation exchange resin in the acid form to obtain an ion exchange of the lithium from the ore. The Li-containing resin is separated from the ore material and the Li is recovered from the resin by e.g., eluting with caustic to get lithium hydroxide. The resin may then be regenerated with an acid to revert back to the acid form.
U.S. Pat. No. 2,980,499 shows improvement over U.S. Pat. No. 2,980,498 above, by contacting the ore with the strongly acidic cation exchange resin at a temperature between 95.degree. C. and 150.degree. C.
U.S. Pat. No. 3,295,920 shows improvement over U.S. Pat. No. 2,980,499 above by contacting the ore and the ion exchange resin in the presence of an aqueous solution containing about 10 to 80% of acetic or propionic acid.
U.S. Pat. No. 3,268,290 shows recovering Li values from sludge which comes from certain electrolytic processes for magnesium production. The lithium recovery involves the use of a short-chain aliphatic monohydric alcohol, heat and agitation to dissolve the Li away from the other components of the sludge, then evaporating the alcohol to obtain LiCl.
It can be seen, then, that there is a recognized need for methods of recovering Li from brines or other aqueous mixtures and solutions which contain metal values other than Li.
The art teaching the formation of lithium aluminate complexes and the use of cation exchange resins to remove Li values from aqueous brines is believed to be the art most pertinent to the present invention.
It is an object of the present invention to provide an ion exchange method of preferentially removing Li values from brines wherein the ion exchange material is long-lived and does not require acid treatment to revert it to the acid form.
Another object is to provide an ion exchange method for preferentially recovering Li values from brines which also contain other metal values.
A further object is to provide an ion exchange resin having incorporated therein LiX.2Al(OH).sub.3 which, after having LiX partially removed and then contacted with brines containing Li salt and other metal salts, will preferentially form a complex with the Li salt while substantially excluding the other metal salts.
Yet another object is to incorporate LiX.2Al(OH).sub.3 in an anion exchange resin in such fashion that Li.sup.+ may be cyclically removed from brine by the resin and then eluted from the resin, the cycle being performed numerous times before encountering appreciable loss of exchange capacity.